Frequent database rebuilds for greylisting

Gary Mills mills@cc.UManitoba.CA
Mon Dec 8 17:33:33 UTC 2003

On Mon, Dec 08, 2003 at 09:28:43AM -0700, Vernon Schryver wrote:
> ] To enlarge on this idea, is there a timestamp associated with each
> ] record?  If so, could dccd set the timestamp to some magic value for
> ] deleted records?  Then, dccd could ignore those records when responding
> What happens now is that the target counts of deleted records are
> set to zero.

That makes sense.

> The DCC database does things that are impossible in other databases.
> For example, the main database on one of your systems has about 10
> million keys for probably 20 million globs of data.  It uses only
> 450-600 MBytes and achives millisecond reads, additions, and updates.
> Any other database you are likely to find would need at least 10 times
> the disk storage and be more than 3 orders of magnitude slower.  Even
> the 40 times less data for a grey list for your installation would be
> a major strain for other schemes.  However, that performance comes at
> the cost of equally great restrictions on flexibility.  The DCC database
> is not a database as most users think of the word.

Ah, that's an impressive design.  I can see that it's a specialized

> I will look for a way to avoid the dbcleaning for ordinary greylist
> operations, because I realize that it is impolitic.  However, it
> would be nice to know if they are a major technical problem and so
> urgent.

I wouldn't call it urgent.  Greylisting seems to be behaving well
this morning.  I'm seeing about 30% DCC rejections and about 30%
DCC embargoes in the sendmail logs.  I was just concerned that doing
a database rebuild that frequently could be a major performance
problem.  So far, it appear not to be.

-Gary Mills-    -Unix Support-    -U of M Academic Computing and Networking-

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